灌木植被分布区阻力特性理论及试验研究

为探明河道灌木植被分布区阻水规律，对灌木植被主干、分枝产生的水流阻力特性及其定量特征进行研究。提出原型植被体积修正系数和灌木植被水力半径确定方法，理论推导灌木植被阻力系数计算公式，并结合水槽试验建立植被阻力系数与植被水力半径为特征长度的植被雷诺数之间的关系式。研究结果表明：引入原型植被体积修正系数和灌木植被水力半径使灌木植被阻力计算更为准确；植被阻力系数与植被雷诺数之间呈指数函数关系，随植被雷诺数的增加呈单调减小的趋势，与水槽试验结果吻合很好。     

Review of the Late Cretaceous-early Paleogene crocodylomorphs of Europe: Extinction patterns across the K-PG boundary

Although the European dinosaur succession during the latest Cretaceous and its relationship with the Cretaceous-Paleogene (K-Pg) mass extinction has been the focus of recent work, other continental vertebrates, such as crocodylomorphs, have received less attention. The European continental record of crocodylomorphs in general, and of eusuchians in particular, is relatively dense through the Maastrichtian until the K-Pg boundary. Traditionally it has been argued that continental crocodylomorphs were minimally impacted by the K-Pg extinction, but they were substantially affected in Europe with the disappearance of endemic eusuchians such as Hylaeochampsidae, Allodaposuchus and their close relatives, and non-eusuchians such as Doratodon or Theriosuchus. Despite extensive sampling in Danian continental deposits, only scarce fragmentary crocodylomorph remains have been cited. It is not until the late Paleocene and Eocene that a recovery in continental crocodylomorphs is observed. The presence of taxa such as planocraniids, the alligatoroids Diplocynodon and Hassiacosuchus, and stem crocodyloids during this period provide the first reliable continental records of Crocodylia in Europe and is best explained by post-extinction immigration from Asia or North America. By contrast, marine forms such as Thoracosaurus are found on both sides of the K-Pg boundary in Europe. The adaptation of these marine animals to different environments, from shallow seas to more transitional or fluvial environments, could be the key to their success and survival across the K-Pg boundary, as seen in other marine crocodylomorph clades such as Dyrosauridae.     

The Hell Creek Formation and its contribution to the Cretaceous–Paleogene extinction: A short primer

Although it represents but one geographic data point, the uppermost Maastrichtian Hell Creek Formation (HCF), exposed in the upper Great Plains of the North American craton, remains the most studied source for understanding the final ∼1.5 Myr of the Mesozoic Era in the terrestrial realm. Because it lies conformably below the earliest Paleocene Fort Union Formation, and together these two units preserve a rich fauna and flora, much of what is understood about the terrestrial Cretaceous–Paleogene (K–Pg) boundary comes from this sequence.The HCF has been reconstructed as an expansive, fluvially drained, low coastal plain, built out, to the west, against the Laramide Orogen, and to the east, against the ultimate transgression (Cannonball) of the Western Interior Sea. Its meandering rivers and moist soils supported a multi-tiered angiosperm-dominated flora and rich insect and vertebrate faunas, including dinosaurs, crocodilians, squamates, turtles, and mammals. A dramatic facies change representing the initiation of catastrophic flooding is preserved, within available levels precision, at the K–Pg boundary.High-precision stratigraphy has proven difficult in this lenticular fluvial system. Where present, the boundary can be recognized by the bipartite boundary claystone; otherwise, palynostratigraphy has proven a powerful tool. Numerical dates have been successfully obtained from in tonsteins at the boundary and above, in the Fort Union; however, these have proven elusive below the boundary within the HCF. The K–Pg boundary in this region is dated at 66.043 Ma (Renne et al., 2013). Magnetostratigraphic studies have been carried out in the HCF; although all but one have lacked numerical dates, these have been used for correlations of widespread, disjunct exposures and for the estimation of sedimentation rates.The palynoflora is largely homogenous through the HCF; at the K–Pg boundary, it shows an abrupt ∼30% extinction. This makes it a powerful tool for identification of the K–Pg boundary, although because the boundary is identified on absence of Cretaceous taxa rather than presence of earliest Paleocene taxa, several competing methods have been applied to identifying the K–Pg boundary using pollen.The macroflora, consisting largely of leaves, consists of three successive floras, showing increasing diversity through the HCF. The ultimate of these three floras undergoes an abrupt 57% extinction; taken as a whole, however, the macroflora undergoes a 78% extinction at the K–Pg boundary.The best data available for dinosaurs – including archaic Aves – show an abrupt extinction. By contrast, salamanders and other lissamphibians, as well as chelonians, cross the boundary virtually without perturbation. Squamates appear to have suffered significant extinctions at the K–Pg boundary, as did euselachians (elasmobranchs) and insects. Mammals suffered a 75% extinction; however, some of this figure cannot be shown to have occurred in less than the last 500 kyr of the Cretaceous, and thus has been potentially attributable to causes other than a bolide impact. Taken together, the survivorship patterns are concordant with the catastrophic inception of ubiquitous flooding characterizing the K–Pg boundary.While the key K–Pg boundary question in the HCF was once the rate of the biotic extinction, it has moved to the distinction between single-cause scenarios, with the Chicxulub bolide as agent of extinction, and multi-cause scenarios, uniting habitat partitioning, Deccan flood-basalt volcanism, climate change, competition, and bolide impact. Not every potential environmental perturbation need be a mechanism for the extinction: parsimony and the data continue to be concordant with a bolide impact as the single agent of the terrestrial K–Pg mass extinction.     

可渗透反应墙对重金属离子Pb~(2+)、Cd~(2+)吸附效果的试验研究

以受尾矿库渗滤液重金属离子Pb2+、Cd2+污染的地下水为研究对象,用天然矿物材料红辉沸石与膨润土作为反应渗透墙(PRB)的活性介质填充材料,试验结果表明,膨润土∶红辉沸石=1∶7,PRB渗透系数处于10-4cm/s数量级且随时间下降最为缓慢;PRB对单一组分Pb2+和单一组分Cd2+去除率分别达99.95%和99.995%;但在双组分PRB体系中,重金属离子Pb2+的存在显著地抑制了PRB对Cd2+的吸附作用,优先选择性吸附顺序是Pb2+Cd2+。     

不同介质材料组合可渗透反应墙渗透性能试验研究

渗透系数是可渗透反应墙(PRB)正常运行的关键参数之一,与PRB活性填充材料的选择密切相关。本试验采用常水头渗透系数测试法,首先选用斜发沸石、红辉沸石为作为PRB的活性介质材料,考察了沸石矿物的类型和粒径对PRB渗透系数的影响,试验结果显示,同一粒径的斜发沸石PRB和红辉沸石PRB渗透系数相差一个数量级;处于同一数量级渗透系数沸石PRB,斜发沸石的粒径大于红辉沸石的粒径。在此基础上,以膨润土作为掺和活性介质材料,讨论了渗透系数处于同一数量级沸石PRB,掺和比例对渗透系数的影响,结果表明,膨润土的掺和能导致沸石PRB渗透系数量级上的差异,与斜发沸石相比,红辉沸石更有利于实现沸石PRB系统渗透系数的可调性。     

径流还原计算中淤地坝拦蓄水量还原计算方法

黄土高原地区淤地坝分布密集,对天然产汇流过程扰动较大,给径流还原或水资源评价带来了极大的影响。因此,研究淤地坝影响下的径流还原计算方法对区域水资源评价或径流设计有重要意义。以黑木头川流域为研究对象,分别采用还原系数法和径流系数法计算了殿市水文站控制产汇流区的淤地坝逐年拦蓄水量,并将两种方法的结果进行对比,论证了还原系数法的适用性。还原系数法的计算结果表明:1971~2007年殿市水文站产流区内的淤地坝平均年拦蓄水量为86.21×104m3,与径流系数法计算所得到的拦蓄水量基本一致,相对误差仅为1.36%。同时,研究发现单位控制面积分摊后的拦蓄水量在年际变化上并不显著,基本维持在某一区间内。研究结果表明还原系数法不仅可用于洪水还原,也可较为准确地计算淤地坝影响区的淤地坝拦蓄变量。作为河川径流还原计算方法或淤地坝影响的黄土高原地区水资源评价研究的计算方法之一,可与径流系数法进行交叉验证,进而获得比较准确的淤地坝拦蓄水量。且由于淤地坝年拦水量空间分摊后,单位控制面积的拦水量基本稳定,故在淤地坝上游无明显人类活动的情况下,可据此初估已知或近似区域淤地坝控制流域面积条件下的淤地坝年拦蓄水量,为黄土高原地区今后开展水资源评价和径流预报提供一条简单的途径。     

海岸破碎带植物消浪数值模拟研究

沿海防浪林能形成柔性的植物消浪体系,可以有效降低风暴潮灾害。由于防浪林消浪效果受波浪、近岸水深及植物等多重因素的影响,消浪机理较为复杂,以往的系统研究成果较少。本文以立面二维自由面紊流模型为工具,建立了基于植物冠层特征的多孔介质模型,精细地模拟了破碎波对植物带的冲击,并与物理模型试验结果进行了对比验证,计算分析了植物带宽度、植物密度、滩地水深等因素对消浪效果的影响。     

Swelling model study of expansive soil at K-0 and triaxial stress stateEI北大核心CSCD

A series of swelling tests is performed on a typical Nanyang expansive soil with medium swelling capacity compacted at various initial densities and water contents. The swelling tests are separately conducted using the conventional oedometer to confine the lateral swelling of the soil specimens, and using the GDS triaxial apparatus to allow the free volumetric swelling. The multiple nonlinear mathematical method is adopted to obtain the lateral swelling model (i.e. K-0 model), which fully considers the coupled effect of initial degree of compaction, moisture content and overburden pressure on the swelling strain. Also, an empirical model for the relationship between spherical stress and volumetric strain is proposed by triaxial swelling test. Based on the K-0 swelling model, a formula is proposed to quantitatively evaluate the swell potential, and also a theoretical calculation method is derived to determine the processing layer thickness of expansive soil slope. Based on the assumption that volumetric swelling strain only changes with spherical stress and is not affected by the deviatoric stress, the correlations between the K-0 model and triaxial model are analyzed, and a method to calculate the volumetric swelling strain by only employing the K-0 model is given. Experimental results show that the proposed K-0 model with multifactor coupling is reasonable to predict the swelling potential of compacted expansive soil. It is found that the key factor to link the K-0 model and triaxial swelling model is assuming an average static lateral pressure coefficient. The average static lateral pressure coefficient tends to decreases with increasing overburden pressure by inversion method. This tendency of average static lateral pressure coefficient is believed to rely on the fact that lateral swelling pressure decreases with the increase of overburden pressure.     

基于初始规划网的镶嵌线自动生成方法研究

针对地理国情普查底图制作过程中数据量大、时间紧、采用传统的镶嵌线生成方法费时费力等问题,提出了基于初始规划网的镶嵌线自动生成法。该方法先利用顾及面要素法和泰森多边形获得初始规划网,然后利用相关系数算法选择最优镶嵌线,最后进行接边纠正。研究表明,该方法可完全满足地理国情普查DOM制作的精度要求,且能大大提高DOM的生产效率。     

基于产业结构视角的云南省县域经济差异研究

基于云南省1992~2012年统计年鉴数据,采用偏离份额分析、基尼系数产业分解方法,分析产业结构演变对云南省县域经济差异的影响。结果表明：云南省县域经济差异受到产业结构偏离和竞争偏离影响较大,滇中县域在产业结构上优势显著,但相对竞争力较弱。滇西和滇南县域竞争优势明显,但不具结构优势;最近10 a来,滇东县域在产业结构、竞争力方面占优,与滇西和滇南县域的差异拉大;从基尼系数产业分解结果看,第二产业是导致云南省县域经济差异扩大的首要因素。此外,第三产业对县域经济差异贡献不断加大,对县域发展不平衡影响日益凸显;产业基尼系数变化分解结果揭示,产业集中效应扩大了县域经济差异,而结构效应则可以缩小县域经济差距,据此提出以产业结构调整来协调县域经济发展的政策建议。